Bodies of water, such as ponds, basins, reservoirs, and lagoons are used to treat waste. Aerobic and anaerobic activities of certain bacteria is one way of treating waste. However, the byproducts of certain anaerobic bacteria give off unpleasant odors. Aerobic bacteria produce carbon dioxide as a byproduct, which does not produce such noxious odors. At times, the oxygen content of the water is insufficient to support the bacterial activity. Aeration increases the amount of oxygen in the wastewater. Certain methods of aeration, such as air diffusion, produce bubbles at the surface of the aerated body of water.